This invention relates to a method of reclaiming used foundry sand and, more particularly to sodium silicate bonded sand resulting from foundry casting methods.
An especially vexing problem has been the cost of purchasing new zircon sand and the disposition of the used zircon sand. Current prices of zircon sand can run $450/ton. Then, when used, an environmental problem occurs. Since this sand is at least mildly radioactive, the location of a dump site is difficult. Heat recovery processes are almost economically prohibitive, viz., energy intensive, and previous "wet" sand processes have not worked satisfactorily.
I have found that a sequence of steps results in the satisfactory reclamation of sand (both the above-mentioned zircon sand and silica sand or any sand that is bonded with a water soluble binder), which include: delumping, mechanical scrubbing, water washing to provide a sand/water slurry, pressure filtration and drying.
Details and advantages of the invention can be seen in the ensuing specification. The invention is described in conjunction with the accompanying drawing which is a block diagram of the steps involved.